| 1 | /*␊ |
| 2 | * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.␊ |
| 3 | *␊ |
| 4 | * @APPLE_LICENSE_HEADER_START@␊ |
| 5 | * ␊ |
| 6 | * Portions Copyright (c) 1999-2003 Apple Computer, Inc. All Rights␊ |
| 7 | * Reserved. This file contains Original Code and/or Modifications of␊ |
| 8 | * Original Code as defined in and that are subject to the Apple Public␊ |
| 9 | * Source License Version 2.0 (the "License"). You may not use this file␊ |
| 10 | * except in compliance with the License. Please obtain a copy of the␊ |
| 11 | * License at http://www.apple.com/publicsource and read it before using␊ |
| 12 | * this file.␊ |
| 13 | * ␊ |
| 14 | * The Original Code and all software distributed under the License are␊ |
| 15 | * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER␊ |
| 16 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,␊ |
| 17 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,␊ |
| 18 | * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. Please see the␊ |
| 19 | * License for the specific language governing rights and limitations␊ |
| 20 | * under the License.␊ |
| 21 | * ␊ |
| 22 | * @APPLE_LICENSE_HEADER_END@␊ |
| 23 | */␊ |
| 24 | /**************************************************************␊ |
| 25 | LZSS.C -- A Data Compression Program␊ |
| 26 | ***************************************************************␊ |
| 27 | 4/6/1989 Haruhiko Okumura␊ |
| 28 | Use, distribute, and modify this program freely.␊ |
| 29 | Please send me your improved versions.␊ |
| 30 | PC-VAN SCIENCE␊ |
| 31 | NIFTY-Serve PAF01022␊ |
| 32 | CompuServe 74050,1022␊ |
| 33 | ␊ |
| 34 | **************************************************************/␊ |
| 35 | /*␊ |
| 36 | * lzss.c - Package for decompressing lzss compressed objects␊ |
| 37 | *␊ |
| 38 | * Copyright (c) 2003 Apple Computer, Inc.␊ |
| 39 | *␊ |
| 40 | * DRI: Josh de Cesare␊ |
| 41 | */␊ |
| 42 | ␊ |
| 43 | #include "sl.h"␊ |
| 44 | ␊ |
| 45 | #define N 4096 /* size of ring buffer - must be power of 2 */␊ |
| 46 | #define F 18 /* upper limit for match_length */␊ |
| 47 | #define THRESHOLD 2 /* encode string into position and length␊ |
| 48 | if match_length is greater than this */␊ |
| 49 | //#define NIL N /* index for root of binary search trees */␊ |
| 50 | ␊ |
| 51 | int␊ |
| 52 | decompress_lzss(u_int8_t *dst, u_int8_t *src, u_int32_t srclen)␊ |
| 53 | {␊ |
| 54 | /* ring buffer of size N, with extra F-1 bytes to aid string comparison */␊ |
| 55 | u_int8_t text_buf[N + F - 1];␊ |
| 56 | u_int8_t *dststart = dst;␊ |
| 57 | u_int8_t *srcend = src + srclen;␊ |
| 58 | int i, j, k, r, c;␊ |
| 59 | unsigned int flags;␊ |
| 60 | ␊ |
| 61 | dst = dststart;␊ |
| 62 | for (i = 0; i < N - F; i++)␊ |
| 63 | text_buf[i] = ' ';␊ |
| 64 | r = N - F;␊ |
| 65 | flags = 0;␊ |
| 66 | for ( ; ; ) {␊ |
| 67 | if (((flags >>= 1) & 0x100) == 0) {␊ |
| 68 | if (src < srcend) c = *src++; else break;␊ |
| 69 | flags = c | 0xFF00; /* uses higher byte cleverly */␊ |
| 70 | } /* to count eight */␊ |
| 71 | if (flags & 1) {␊ |
| 72 | if (src < srcend) c = *src++; else break;␊ |
| 73 | *dst++ = c;␊ |
| 74 | text_buf[r++] = c;␊ |
| 75 | r &= (N - 1);␊ |
| 76 | } else {␊ |
| 77 | if (src < srcend) i = *src++; else break;␊ |
| 78 | if (src < srcend) j = *src++; else break;␊ |
| 79 | i |= ((j & 0xF0) << 4);␊ |
| 80 | j = (j & 0x0F) + THRESHOLD;␊ |
| 81 | for (k = 0; k <= j; k++) {␊ |
| 82 | c = text_buf[(i + k) & (N - 1)];␊ |
| 83 | *dst++ = c;␊ |
| 84 | text_buf[r++] = c;␊ |
| 85 | r &= (N - 1);␊ |
| 86 | }␊ |
| 87 | }␊ |
| 88 | }␊ |
| 89 | ␊ |
| 90 | return dst - dststart;␊ |
| 91 | }␊ |
| 92 | |
